1. Field of the Invention
This invention relates to novel inhibitors of type I receptor tyrosine kinases and related kinases, pharmaceutical compositions containing the inhibitors, and methods for preparing these inhibitors. The inhibitors are useful for the treatment of hyperproliferative diseases, such as cancer and inflammation, in mammals and especially in humans.
2. Description of the State of the Art
The type I receptor tyrosine kinase family consists of four closely related receptors: EGFR (ErbB1 or HER1), ErbB2 (HER2), ErbB3 (HER), and ErbB4 (HER4) (Reviewed in Riese and Stern, Bioessays (1998) 20:41-48, Olayioye et al., EMBO Journal (2000) 19:3159-3167 and Schlessinger, Cell (2002) 110:669-672). These are single pass transmembrane glycoprotein receptors containing an extracellular ligand binding region and an intracellular signaling domain. In addition, all receptors contain an intracellular active tyrosine kinase domain with the exception of ErbB3 whose kinase domain does not exhibit enzymatic activity. These receptors transmit extracellular signals through the cytosol to the nucleus upon activation. The activation process is initiated by ligand binding to the extracellular domain of the receptor by one of a number of different hormones. Upon ligand binding, homo- or heterodimerization is induced which results in the activation of the tyrosine kinase domains and phosphorylation of tyrosines on the intracellular signaling domains. Since no known ligand for ErbB2 has been described and ErbB3 lacks an active kinase domain, these receptors must heterodimerize to elicit a response. The phosphotyrosines then recruit the necessary cofactors to initiate several different signaling cascades including the ras/raf/MEK/MAPK and PI3K/AKT pathways. The precise signal elicited will depend on what ligands are present since the intracellular signaling domains differ as to what pathways are activated. These signaling pathways lead to both cell proliferation and cell survival through inhibition of apoptosis.
Several investigators have demonstrated the role of EGFR and ErbB2 in development and cancer (Reviewed in Salomon, et al., Crit. Rev. Oncol. Hematol. (1995) 19:183-232, Klapper, et al., Adv. Cancer Res. (2000) 77, 25-79 and Hynes and Stern, Biochim. Biophys. Acta (1994) 1198:165-184). Squamous carcinomas of the head and neck, and lung express high levels of EGFR. Also, constitutively active EGFR has been found in gliomas, breast cancer and lung cancer. ErbB2 overexpression occurs in approximately 30% of all breast cancer. It has also been implicated in other human cancers including colon, ovary, bladder, stomach, esophagus, lung, uterus and prostate. ErbB2 overexpression has also been correlated with poor prognosis in human cancer, including metastasis, and early relapse.
The type I tyrosine kinase receptor family have been an active area of anti-cancer research (Reviewed in Mendelsohn and Baselga, Oncogene (2000) 19:6550-6565 and Normanno et al., Endocrine-Related Cancer (2003) 10:1-21). Several inhibitors of the EGFR and the ErbB2 signaling pathway have demonstrated clinical efficacy in cancer treatment. Herceptin, a humanized version of anti-ErbB2 monoclonal antibody, was approved for use in breast cancer in the United States in 1998. Iressa and Tarceva are small molecule inhibitors of EGFR that are expected to be commercially available. In addition, several other antibodies and small molecules that target the interruption of the type I tyrosine kinase receptor signaling pathways are in clinical and preclinical development. For example, IMC-225, which is a humanized antibody against the extracellular domain of EGFR demonstrated efficacy and will likely be approved.